1. Field of the Invention
This invention relates to an image forming apparatus, and more particularly pertains to a mechanism for moving a sheet separator member in an axial direction of a roller to separate a sheet from the roller in an image forming apparatus.
2. Description of the Related Art
Heretofore, there has been known an image forming apparatus such as an electrophotographic copying machine and a printer provided with a fixing device in which a sheet is nipped by a nip portion of a fixing roller unit comprising a heater roller and a presser roller to fix an image on the sheet by heat/press operation of the fixing roller unit. A pawl-like sheet separator member is provided at such a position on the heater roller and the presser roller as to come into contact therewith at a certain contact pressure in order to keep a sheet from undesirably winding around the heater roller and the presser roller.
The fixing roller unit provided with such a sheet separator member has suffered from the following drawbacks. A long-time contact of the separator member with the heater roller (or the presser roller) at the same location may damage the surface of the roller due to abrasion or frictional resistance with the sheet separator member. Furthermore, as toner particles intrude into a space between the roller surface and the sheet separator member and resultantly deposit on the sheet separator member, abrasion is progressed, and damage on the roller surface becomes serious. In addition, redundant toner particles may adhere on a sheet under image fixation with the result that the sheet may be smeared or jammed.
In order to prevent such a drawback, there has been proposed an image forming apparatus provided with a thrust driving mechanism for moving a sheet separator member in an axial direction of the roller while keeping the sheet separator member in contact with the surface of the roller in an attempt to shorten a period for contacting the sheet separator member at the same location on the roller surface.
The aforementioned image forming apparatus, however, requires a drive source such as a solenoid, in addition to a drive source for driving a fixing roller unit, so as to move the sheet separator member with use of the thrust driving mechanism, which raises production cost of the apparatus. Also, there has been proposed a driving mechanism of a so-called xe2x80x9cone-way-bearing typexe2x80x9d to transversely move the sheet separator member by utilizing a driving force of a drive source for a fixing roller unit. However, the arrangement of such a driving mechanism is complicated, which resultantly raises production cost of the apparatus.
In view of the above, it is an object of the invention to provide an image forming apparatus free from the problems residing in the prior art. It is a further object of this invention to provide an image forming apparatus equipped with a mechanism that enables to move a sheet separator in an axial direction of a roller without providing a drive source dedicatedly used for moving the sheet separator and with a simplified construction to thereby reduce production cost of the apparatus.
According to an aspect of this invention, an image forming apparatus comprises a pair of fixing rollers which are rotated to fix an image on a sheet; a sheet separator which is rendered into contact with at least one of the fixing rollers to separate the sheet from the roller; and drive means which converts a driving force of a drive source for rotating the fixing roller or a transport roller disposed downstream in a sheet transport direction with respect to the fixing roller pair to a driving force in an axial direction of the fixing roller so as to reciprocate the sheet separator in the axial direction of the fixing roller.
In this arrangement, utilizing the driving force of the drive source for rotating the fixing roller or the transport roller enables to reciprocate the sheet separator in the axial direction of the roller. This arrangement eliminates necessity of providing an additional drive source for reciprocating the sheet separator. Thus, this arrangement simplifies the construction of reciprocating the sheet separator in the axial direction of the roller while reducing production cost of the apparatus.
These and other objects, features and advantages of the present invention will become more apparent upon a reading of the following detailed description and accompanying drawing.